08000 322 122
United Kingdom
1800 322 122
Republic of Ireland

Floor Insulation: Insulating solid ground floors with a timber floating floor

Sand blinding and hardcore

Concrete slab

Randon barrier / DPM

Read more

Quinn Therm QF PIR Insulation Boards/Quinn Lite Pac EPS Boards

Read more

Timber flooring on polyethylene slip sheet

Read more

Internal finish

Read more

  • Sand blinding and hardcore

  • Concrete slab

  • Randon barrier / DPM

    Read more

  • Quinn Therm QF PIR Insulation Boards/Quinn Lite Pac EPS Boards

    Read more

  • Timber flooring on polyethylene slip sheet

    Read more

  • Internal finish

    Read more

A floating timber floor is commonly used in domestic retrofit or refurbishment projects as the timber battens or joists are laid on top of the existing concrete slab, so there is no need to remove the existing floor surface.

It is an excellent way of improving the thermal performance of an existing property as installing thermal insulation above the slab isolates the thermal mass of the slab from the building interior, giving the building a rapid thermal response. It offers a good solution for upgrading the thermal performance of an uninsulated concrete floor.

Speed and ease of installation also make this a popular floor insulation method, with no need for wet trades and no drying time required. 

When upgrading an existing floor, it is important to consider the impact of the change of floor levels on doors and thresholds.

How to install floor insulation in a timber floating floor

1. Ensure the concrete slab is fully dried out, level and free from projections. The floor should have no more than a 5mm deflection over 2m if using Quinn Therm PIR insulation boards and no more than 35mm deflection over 3m if using Quinn Lite Pac EPS insulation.

2. Lay the appropriate damp proof membrane (DPM) over the concrete slab, ensuring it is well lapped and folded and is sealed to the wall’s damp proof course (DPC). Where radon control measures are required, the specified DPM should be gas resistant.

3. Lay insulation boards in a continuous layer across the whole floor. The boards should be butted tightly together and laid with joints staggered between rows. Boards should be cut neatly around service penetrations to minimise heat loss through thermal bridging.

4. Install preservative treated timber battens where high point loads are expected, for example at thresholds. The top of the battens should be at the same level as the top of the insulation boards.

5. Overlay the insulation boards with a polyethene slip sheet taped at the joints. The sheet should have 150mm overlaps and should be turned up 100mm at the walls.

6. The timber floor can now be laid over the polyethylene sheet.

Required insulation thickness of Quinn Therm QF:

Perimeter / Area ratio
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Thickness (mm) U-value (W/m2K)
50 0.15 0.21 0.24 - - - - - - -
60 0.14 0.19 0.21 0.23 0.24 0.25 - - - -
70 0.13 0.17 0.19 0.21 0.22 0.23 0.23 0.24 0.24 0.24
75 0.12 0.16 0.18 0.20 0.21 0.21 0.22 0.22 0.23 0.23
80 0.12 0.16 0.18 0.19 0.20 0.21 0.21 0.21 0.22 0.22
90 0.12 0.15 0.16 0.18 0.18 0.19 0.19 0.19 0.20 0.20
100 0.11 0.14 0.15 0.16 0.17 0.17 0.18 0.18 0.18 0.18
110 0.10 0.13 0.14 0.15 0.16 0.16 0.16 0.16 0.17 0.17
120 0.10 0.12 0.13 0.14 0.15 0.15 0.15 0.15 0.15 0.16
125 0.10 0.12 0.13 0.14 0.14 0.14 0.15 0.15 0.15 0.15
140 0.09 0.11 0.12 0.13 0.13 0.13 0.13 0.13 0.14 0.14
150 0.09 0.10 0.11 0.12 0.12 0.12 0.13 0.13 0.13 0.13
160 0.08 0.10 0.11 0.11 0.12 0.12 0.12 0.12 0.12 0.12
180 0.08 0.09 0.10 0.10 0.10 0.11 0.11 0.11 0.11 0.11
200 0.07 0.08 0.09 0.09 0.10 0.10 0.10 0.10 0.10 0.10

U-value results above based upon floor construction shown:

150mm concrete; radon barrier / DPM; Quinn Therm QF; timber flooring (floor finish omitted); Calculations performed to BS EN ISO 6946 and BS EN ISO 13370, taking account of repeating thermal bridges.

Required insulation thickness of Quinn Lite PAC EPS Pearl:

Perimeter / Area ratio

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Thickness (mm)
75 0.14 0.20 0.23 0.25 0.26 0.27 0.28 0.28 0.29 0.29
80 0.14 0.19 0.22 0.24 0.25 0.26 0.27 0.27 0.27 0.28
90 0.13 0.18 0.20 0.22 0.23 0.24 0.24 0.25 0.25 0.26
100 0.13 0.17 0.19 0.20 0.21 0.22 0.23 0.23 0.23 0.24
110 0.12 0.16 0.18 0.19 0.20 0.21 0.21 0.22 0.22 0.22
120 0.12 0.15 0.17 0.18 0.19 0.20 0.20 0.20 0.20 0.20
125 0.12 0.15 0.16 0.18 0.18 0.19 0.19 0.19 0.20 0.20
130 0.11 0.14 0.16 0.17 0.18 0.18 0.19 0.19 0.19 0.19
140 0.11 0.14 0.15 0.16 0.17 0.17 0.18 0.18 0.18 0.18
150 0.10 0.13 0.15 0.15 0.16 0.16 0.17 0.17 0.17 0.17
160 0.10 0.13 0.14 0.15 0.15 0.15 0.16 0.16 0.16 0.16
170 0.10 0.12 0.13 0.14 0.14 0.15 0.15 0.15 0.15 0.15
175 0.10 0.12 0.13 0.14 0.14 0.14 0.15 0.15 0.15 0.15
180 0.09 0.12 0.13 0.13 0.14 0.14 0.14 0.14 0.15 0.15
190 0.09 0.11 0.12 0.13 0.13 0.13 0.14 0.14 0.14 0.14
200 0.09 0.11 0.12 0.12 0.13 0.13 0.13 0.13 0.14 0.13

Need technical support?

For help and advice on any of our products and how they might fit your needs please contact our Technical by Quinn team.

  • Floor Insulation
  • Pitched Roof Insulation
  • Flat Roof Insulation
  • Wall Insulation